The present transportation intensive phase of the Industrial Revolution has produced an inventory of about 1-billion internal combustion engines that have been designed for operation with gasoline or diesel fuel. This population of engines is mostly comprised of four-stroke or cycle types and, to a lesser extent, two-stroke or cycle types of reciprocating piston designs. Cyclic operation of intake, compression, power, and exhaust events characterize both types of engines.
Gasoline and diesel fuels have been proven to be objectionable to the environment. These fossil fuels are unacceptable because of toxic emissions that cause smog and particulate-related diseases in congested traffic areas along with climate changes and global warming. Because such fuels comprise portions of civilization's dependence upon burning more than a million years' of finite fossil fuel accumulations each year, for most of the world's population, continued depletion causes economic insecurity and inflation, balance of trade deficits, hardship, and conflicts for control of remaining supplies.